Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Abanico aluvial del arroyo Matomí, Baja California ; análisis lítológico, geomorfológico, multitemporal y espectral

Auteur : Lino Escobedo, Luz Selene

Etablissement de soutenance : Centro de Investigación Científica y de Educación Superior de Ensenada Baja California (CICESE)

Grade : Maestro en Ciencias de la Tierra con especialidad en Geología 2006

Résumé
The arroyo Matomi alluvial fan is located to the Northeast of Baja California peninsula, at the foothillsof the Gulf of California escarpment, where sediments from the Matomi, Canelo and Cantera basinsare deposited, with catchment areas of 545, 307 and 152 Km² respectively. Sediment contributions insuch basins are from Paleozoic to Cretaceous metasedimentary and batholitic rocks, Miocenevolcanoclastic rocks, Pliocene marine and non-marine sediments, and Quaternary alluvial deposits.Despite the arid climate in the study area, with scarce vegetation and low mean annual rainfall (<100mm), the area is subject to occasional intense precipitation events, e.g. Hurricane Nora in 1997, inwhich the nearest meteorological station registered 300mm in 24 hours. The Nora effects are exploredby means of a multitemporal analysis of 3 Landsat images : 2 prior to the event (1987 and 1988) and oneafter the hurricane (2001). False color composites of the Landsat images were photo-interpreted, zonesaffected by a hydrodynamic force were identified, through the disturbance of clasts within the streambed, changing the exposure surface of rocks that had developed dessert varnish, inducing changesbetween images integrated by the sensor before and after the meteorological event. Also, in order tohighlight changes within the alluvial fan, the standard and selective versions of the principalcomponents technique were applied to the multitemporal images.For the lithologic, geomorphologic, and spectral analysis of the alluvial fan, hyper-spectral images fromthe airborne MASTER sensor were used, with 50 spectral bands from the visible (0.44 μm) to thethermal infrared (13 μm). In false color composites of MASTER images with 5m spatial resolution, fieldsampling zones were selected, in which rock content indexes were calculated describing each site’spredominating rocks. For each sampled site in the field, spectral firms registered by the MASTERsensor were extracted. The largest variation in spectral vectors occurs in the visible and reflectiveinfrared spectral region. A geomorphologic map was generated through photo-interpretation of falsecolor composites of a MASTER image mosaic, extracting the braided network of stream beds.Keywords:Arroyo Matomí, alluvial fan, dessert varnish, multitemporal and spectral analysis, geomorphologic,lithologic.

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